There are a handful of ways to produce hydrogen fuel without emitting carbon into Earth’s atmosphere. One involves using electricity to split water into hydrogen and oxygen.

This method, known as electrolysis, requires a catalyst that speeds up chemical reactions that occur within hydrogen fuel cells.

More often than not, this electrocatalyst is platinum, a metal so rare that it’s typically more expensive than gold, which makes the production process more costly than traditional sources of renewable energy and fossil fuels.